Heating apparatuses for comfort purposes are well known, e.g. in the restaurant business and in relation to outside occasions in cold weather in general, to ensure that persons can sit or stand outside and e.g. dine without getting cold. Therefore, heating apparatuses using e.g. gas for heating are commonly known since they are cheap to acquire. However, due to the large energy consumption and low coefficient of utilization of such natural gas driven heaters, these are environmentally unfriendly and expensive in operation. Further, common natural gas driven heaters often have their heat source arranged 2-3 meters above ground to facilitate heating of a larger area, e.g. an area around one or more tables. This is not advantageous since it is often the lower part of the body that gets cold and needs heating, e.g. when sitting around a table, and since it reduces the coefficient of utilization.
US patent application 2007/0267399 deals with this problem by arranging an electrical or a gas driven heater underneath a table. This invention however, has large energy consumption, and it gets too hot so that persons arranged around the table can get burned when touching the gas driven heater.
Japanese patent document JP61076826 relates to a heater comprising a guard made of a material of high thermal conductivity such as copper, to assure that a thermistor attached to the heater can detect heating of the guard and turn off the heat source fast if the guard gets too hot. The inner surface of the guard comprises a heat reflecting material to achieve a lower outer surface temperature of the guard. This invention suffers from the disadvantage that the heat source can still heat up the heat conducting guard, making the control of the heat source necessary, and making the heater rather unreliable.